1.Field of the Invention
The present invention relates to a semiconductor device having a circuit region where semiconductor components such as transistors or the like are formed.
2.Description of the Related Art
Heretofore, semiconductor devices have had a circuit region where circuits such as memories, logic circuits, etc., are formed, and a guard ring for preventing water from entering the circuit region from the surrounding area. The guard ring extends along the periphery of the chip and is made of a metal such as copper (Cu) or the like. One known guard ring is disclosed in Japanese Patent Laid-open Publication No. 45766/97,for example, as follows: A semiconductor device has an outer guard ring disposed near the periphery of a chip and an inner guard ring disposed between the outer guard ring and a circuit region. The outer guard ring and the inner guard ring jointly make up a double guard ring assembly. The double guard ring assembly is advantageous in that even if the outer guard ring is defective, allowing water to enter a region inward of the outer guard ring from outside of the chip, the inner guard ring prevents the water from entering the circuit region.
However, the double guard ring assembly is a mere combination of two guard rings. Therefore, when water happens to enter a region inward of the outer guard ring from outside of the chip through a defect in the outer guard ring, if the inner guard ring has a defect somewhere therein, the water finds its way through the defect in the inner guard ring into the circuit region, tending to corrode circuit interconnections in the circuit region.